In the rapid transfer and positioning of a shuttle or carriage which is supported for reciprocating linear movement, it is known to use an endless or open-ended flat flexible timing belt having longitudinally spaced parallel teeth. The toothed belt extends around a drive sprocket having mating teeth and connected to a drive shaft which is driven by a reversible drive. The toothed timing belt also extends around an idler or tail sprocket having mating teeth and rotatably supported by a tail shaft which extends parallel to the drive shaft. The spacing between the drive shaft and the tail shaft determine the extent of linear travel of the carriage which is commonly supported by parallel spaced tracks.
When the shuttle or carriage positioning and transfer system or apparatus is used for rapidly moving a substantial load, for example, when used with automotive assembly machinery for moving components of automotive vehicles, the load carrying capacity of the timing belt usually determines the load moving capacity of the shuttle or carriage. If two timing belts are used to move a shuttle or carriage, the variation in the belts due to production tolerances, results in one of the belts carrying a greater portion of the load than the other belt. Thus if the one belt is operated at its full rated capacity, the second belt does not significantly increase the load carrying capacity of the belt system, and primarily offers only a safety factor.
The present invention is directed to an improved carriage transfer and positioning system or apparatus which provides for rapidly moving a carriage which is capable of supporting or moving a substantial load along a linear path and for precisely positioning the carriage at predetermined locations along the linear path. In accordance with one embodiment of the invention, a plurality of flat toothed timing belts are positioned in laterally adjacent relation, and each belt has opposite end portions or adjacent portions connected to the carriage by means of relative adjustable belt clamping blocks and plates. The belts extend around a common toothed drive sprocket connected to a head or drive shaft driven by a multiple speed drive preferably having multiple electric motors and oil-shear clutch and brake discs.
The belts also extend around separate or corresponding toothed tail sprockets supported by a tail shaft and wherein the tail sprocket for one belt is free to rotate relative to the adjacent tail sprocket for the other belt. The tension in each belt is adjusted by relative movement by the corresponding clamping blocks in order to obtain substantially equal or uniform tension in the drive belts. The multiple flat toothed belts not only provide a safety factor but provide for moving a substantially greater load with the carriage by operating each belt at its full rated capacity. In one application, one or more of the timing belts are connected to transfer a carriage connected to a plurality of tool trays for shuttling or indexing the trays laterally relative to a product flow or assembly line between storage and working positions or stations. The drive for the belt or belts is located at one end of the belt transfer system to provide the system with a low profile.
Other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.